This invention relates generally to high voltage power class fuses which include load break contacts and more particularly to such fuses which include means for controlling the effects of arc gases created upon manual engagement and disengagement of the load break contacts.
High voltage power class fuses of the type which include load break contacts are most often used to protect high voltage electrical devices, such as, for example, transformers, from excessive electrical loads.
Normally the load break contacts of a power class fuse are mechanically closed and create little if any arc and resulting gases. However, when the load break contacts are closed under fault conditions through the manual insertion of one of the load break contacts into an insulative canister of the fuse, hot arc gases are generated. These arc gases not only create a pressure within the canister, which tends to prevent closure of the contacts, but the gases also contain contaminants such as, for example, metallic particles, which could disrupt the operation of the fuse element of the fuse.
A variety of prior art devices have been included in fuse canisters to control, in some manner, the gases created by the arc produced upon manual closure of the load break contacts. U.S. Pat. No. 3,732,517, issued May 8, 1973, discloses an arc snuffing device including a spring loaded member which closes a deionizing chamber about one of the contacts following separation thereof. In U.S. Pat. No. 3,984,651, issued Oct. 5, 1976, and assigned to the same assignee as the instant invention, a grooved, insulating sleeve is included in the fuse canister to channel arc gases generated for the promotion of turbulence therein and thereby cool the gases. An insulative barrier mounted on the insertable load break contact restricts the gases in the canister to the space surrounding the mated contacts.
In still another U.S. Pat. No. 4,059,816, issued Nov. 22, 1977, and assigned to the same assignee as the instant invention, there is included a load break fuse in which a non-conductive sleeve and collar is formed about the fuse element. A load break contact probe having a non-conductive tip is provided at the inner end of the fuse element. A non-conductive disc is mounted between the fuse element and contact probe. The sleeve, collar and disc serve to diffuse and cool ionized gases generated by arcing between the load break contacts within the canister.
While the above described devices all have been designed to control, in some fashion, hot arc gases created upon engagement of the load break contacts in a power class fuse, each is somewhat complicated and/or requires a plurality of components, adding to the cost thereof. Furthermore, these devices do not control metallic particles and other contaminants normally found in the arc gases when they are generated.